CVE-2025-4120: Netgear JWNR2000v2 Buffer Overflow Flaw

CVE-2025-4120 Overview

A critical buffer overflow vulnerability has been identified in Netgear JWNR2000v2 wireless routers running firmware version 1.0.0.11. The vulnerability exists in the sub_4238E8 function, where improper handling of the host argument allows attackers to trigger a buffer overflow condition. This flaw can be exploited remotely over the network, potentially enabling attackers to execute arbitrary code or crash the affected device.

The vendor was contacted early about this disclosure but did not respond in any way, leaving affected devices without an official patch.

Critical Impact

Remote attackers can exploit this buffer overflow to potentially gain full control of the affected Netgear router, compromising network security and enabling lateral movement within the network.

Affected Products

• Netgear JWNR2000v2 Firmware version 1.0.0.11
• Netgear JWNR2000v2 Hardware

Discovery Timeline

• April 30, 2025 - CVE-2025-4120 published to NVD
• May 13, 2025 - Last updated in NVD database

Technical Details for CVE-2025-4120

Vulnerability Analysis

This vulnerability is a classic buffer overflow (CWE-120) stemming from improper restriction of operations within memory buffer bounds (CWE-119). The sub_4238E8 function in the Netgear JWNR2000v2 firmware fails to properly validate the length of the host argument before copying it into a fixed-size buffer. When an attacker supplies a specially crafted oversized input for the host parameter, the function writes data beyond the allocated buffer boundary, potentially overwriting adjacent memory regions including return addresses and function pointers.

The vulnerability requires low privileges to exploit and does not require user interaction, making it particularly dangerous in exposed network environments. Successful exploitation could allow an attacker to achieve high impact on confidentiality, integrity, and availability of the affected system—potentially gaining complete control over the router.

Root Cause

The root cause of this vulnerability lies in the absence of proper bounds checking within the sub_4238E8 function. The function accepts the host argument without validating its length against the destination buffer's capacity. This classic memory safety issue allows attackers to inject data that overflows the buffer, corrupting memory structures and potentially hijacking program execution flow.

Attack Vector

This vulnerability can be exploited remotely over the network. An attacker with network access to the router's management interface can send a malicious request containing an oversized host parameter value. The attack does not require physical access to the device and can be launched from any network position that can reach the vulnerable service.

The exploitation process involves:

1. Identifying a Netgear JWNR2000v2 router running vulnerable firmware version 1.0.0.11
2. Crafting a request with an oversized host argument to the affected function
3. The buffer overflow overwrites critical memory structures
4. Depending on the payload, the attacker may achieve code execution or cause denial of service

Technical details and proof-of-concept information can be found in the GitHub Buffer Overflow PoC repository.

Detection Methods for CVE-2025-4120

Indicators of Compromise

• Unexpected reboots or crashes of Netgear JWNR2000v2 routers
• Anomalous network traffic patterns to/from the router's management interface
• Unusual outbound connections from the router to unknown external IP addresses
• Modified router configurations or unauthorized administrative accounts

Detection Strategies

• Deploy network intrusion detection systems (IDS) to monitor for oversized HTTP requests targeting Netgear router management interfaces
• Implement deep packet inspection rules to detect malformed host parameter values in requests
• Monitor router syslog output for crash events or memory corruption indicators
• Use SentinelOne Singularity to detect anomalous behavior patterns on network segments containing vulnerable devices

Monitoring Recommendations

• Enable verbose logging on network perimeter devices to capture traffic to router management interfaces
• Implement network segmentation to isolate IoT and router devices from critical network segments
• Deploy continuous vulnerability scanning to identify devices running affected firmware versions
• Configure alerting for any authentication attempts or configuration changes on Netgear devices

How to Mitigate CVE-2025-4120

Immediate Actions Required

• Restrict network access to the router's management interface to trusted IP addresses only
• Disable remote management features if not required
• Place vulnerable routers behind a firewall with strict ingress filtering
• Consider replacing affected devices with supported hardware if no patch becomes available

Patch Information

As of the last update, Netgear has not responded to disclosure attempts and no official patch is available for this vulnerability. Organizations should implement compensating controls and consider device replacement strategies. Monitor the Netgear Official Website for any future security advisories.

For tracking and additional technical intelligence, refer to VulDB #306600.

Workarounds

• Disable remote management access to the router entirely
• Implement network-level access controls to restrict management interface access to specific trusted hosts
• Deploy a network firewall in front of the vulnerable device to filter malicious requests
• Consider network segmentation to isolate the vulnerable router from sensitive network resources
• Monitor network traffic for exploitation attempts using IDS/IPS solutions

# Example: Restrict management interface access using firewall rules
# Block external access to router management port (typically 80/443)
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP